# Homework Help: RLC circuit frequency

1. Nov 20, 2008

### zakaqel

1. The problem statement, all variables and given/known data

A RLC circuit has a resonance frequency of 6 KHz. When it is driven by a 8 KHz ac generator, it has an impedance of 1 k W. What are R, L and C in the circuit?

2. Relevant equations

3. The attempt at a solution

the equation for the resonant frequency will be
fo = 1 / 2 π √(L C)
the equation for the impedence will be
Z = √[R2 + (XL - XC)^2]
where XL = 2 π f L

XC = 1 / 2 π f C
f = 8 x 10^3 Hz
fo = 6 x 10^3 Hz
Z = 1 x 10^3 Ω

How am I supposed to solve for the three unkowns(R,L,C) with only two equations? Is there a third relationship for R?

2. Nov 20, 2008

### LowlyPion

Are you sure there is no impedence at resonance given?

3. Nov 20, 2008

### zakaqel

No impedance at resonance is given. That's what I was thinking...it'll be impossible to solve if you don't have a relation for R.

4. Nov 20, 2008

### dlgoff

Is your circuit series or parallel?
And what is this: "...it has an impedance of 1 k W"? Do you mean kohm of the circuit or the generator?

5. Nov 20, 2008

### LowlyPion

6. Nov 20, 2008

### LowlyPion

I think he used the Latinized W instead of Ω.

7. Nov 20, 2008

### zakaqel

well, the question was given by my professor. I am 100% sure that there is a peice of informaiton missing from the original question.

BTW, the RLC is connected in series.

8. Nov 20, 2008

### zakaqel

It turns out that he forgot to say that the phase angle=45 degrees...ugghhhh....It's an easy one now.

Thanks for the help!

9. Nov 20, 2008

### LowlyPion

Alrighty then. There's your third equation.

Good luck.